Ethanol - E85

[trotty]

Dude u rock!! I have injectors waiting to go in. Was waiting for flex. This will come just at the right time !

 

[Cameron McPherson]

Prototype Flex circuit is built:

View attachment 25217

So just to clarify/recap for those who haven't read through the entire thread (you should though):

The flex fuel sensor which goes in your fuel line just before the fuel rail, sends a signal to this box, which in turn sends a signal to the ecu to change maps to the correct ethanol content - like a dual map setup but with automatic electronic switches instead of manual switches?

 

[BCX]

So just to clarify/recap for those who haven't read through the entire thread (you should though):

The flex fuel sensor which goes in your fuel line just before the fuel rail, sends a signal to this box, which in turn sends a signal to the ecu to change maps to the correct ethanol content - like a dual map setup but with automatic electronic switches instead of manual switches?

Yep, but will add a bit more info and summarise what's already been said.

• Flex sensor will go inline with fuel line. Easiest place to tap in is on the return line.
  
• Flex sensor produces a frequency output based on alcohol content. 50hz = 0% 150hz=100%
• The H8 (MH7202/MH7203) chip uses dedicated inputs that have the ability to read frequency (and other digital signals) like the pulse from your crank/cam sensor, or MAF, etc
• There aren't any available inputs like this to use, and even if there was, changing Mitsubishi's code to suit is hard and time consuming.
• The way around this: most Mitsubishi's have a spare analog-to-digital inputs (ie an input that can read a voltage rather than a certain signal). This input in our case is the secondary o2 sensor.
• The circuit (pictured) just reads in the frequency signal from the Flex Sensor, then outputs a 0-5v voltage which corresponds with the amount of alcohol linearly... 0%=50hz -> 0v, 100%=150hz -> 5v
• Others have implemented this circuit using a dedicated Frequency-to-Voltage chip (LM2907) but I've decided to use an Atmel attiny85 with some custom code... brings the size down of the circuit and can also be updated via software if we need to change it down the track (ie the flex sensors change spec for some reason)
• the flex code that replaces your standard ROM on your ECU reads in this voltage, and uses it as a factor to interpolate between between two maps (high octane "98" map vs Ethanol Map map). So there is about 10 different maps that are modified

Its the fact that the ECU can interpolate between the two values that makes Flex much better than switchable maps. For example, if you had 10 litres of E85 left (lets say it was a good batch and actually had 85% alcohol content), but you're stuck cos there isn't a servo that sold E85 near you... so you decide to just put in another 10 litres of 98 to get you by..

85% / 2 (as you are 'watering it down' with 98) = ~42% alcohol at a guess?

If you had switchable maps... you could leave it on the '85' tune, but ignition timing is usually aggressive and also puts more fuel in, so you'd really run rich for 98... would get you by, but at a cost of performance and fuel economy.

otherwise, you could switch it to the 98 tune, ignition timing is more sensible, but we might not be putting the right amount of fuel in...

Flex gives the ECU the ability to calculate exactly what the target lambda, timing, etc value should be between the two maps. You can pretty much chuck in whatever fuel you want, The ecu will take care of it. Steve might want to elaborate on this example some more...

Hope this helps explain a few things.

Cheers,
Bill

 

[pretzil]

Yeah, I was under the impression the sensor usually went on the return line after the fuel rail.

Out of curiosity, what happens with the interpolation if the sensor reads greater than 85% but you only have an e85 tune? or an e70 tune for that matter?

 

[Cameron McPherson]

That's mad smart, Bill. Good stuff

Was just a little cloudy on how it all works from the chip to the ecu, but that makes a lot of sense now. clever using spare o2 imput too!

 

[BCX]

That's mad smart, Bill. Good stuff

Was just a little cloudy on how it all works from the chip to the ecu, but that makes a lot of sense now. clever using spare o2 imput too!

I cant take credit for that part, Evo guys do the same... My ecu code does what other implementations do, except mines written from scratch with help from Steve, and to tie in with other mods. The ROM will have all the KSMODS1.3 as well as some other goodies of my own.

 

[whats_doing]

Stop. I can only get SO erect!!!!!

 

[pretzil]

Will this work on automatics?

 

[Kaldek]

 

[BCX]

Will this work on automatics?

yeah, no reason it wouldnt.

Only thing at the moment, the ROM i'm modifying is the EM2004/EM2005 based rom. Some autos with TCL have the other one? (EM2428/EM2381)

So will patch the second ROM once the EM2004 is all good.

 

[pretzil]

Thought maybe the same reason switchable maps doesn't work on (some?) autos...

 

[BCX]

Just tested the circuit and flex sensor out of the car... Poured a bit of Jack Daniels into the sensor, voltage shot up to around ~2.3v on my multimeter.

Will hopefully mount the sensor tomorrow and then I'll water down the 98 in my tank with a bit of 85 to see if I can get a small reading and if the ECU can read the voltage.

 

[whats_doing]

You wasted jack??
I'd say shame on you, but it was for a good cause.

 

[BCX]

You wasted jack??
I'd say shame on you, but it was for a good cause.

lol, I don't even drink it... mate left small bit last time he was here. Needed something with decent alcohol content to test it, didnt have any metho.

Anyways, Flex sensor is installed, again the bracket isn't the final design so will fix the original drawing with the mods I had to do to fit it....

will run the wire into the cabin tomorrow...

 

[TME_Steve]

Yeah, I was under the impression the sensor usually went on the return line after the fuel rail.

Out of curiosity, what happens with the interpolation if the sensor reads greater than 85% but you only have an e85 tune? or an e70 tune for that matter?

Aftermarket guys and us included are mounting these in the return, but there seem to be people mounting them in the supply lines also. Putting a sensor unnecessarily under pressure seems dumb, so sticking with the return.

The way we're setting it up, you could tune to whatever the highest content you can get is, set it at that, then extrapolate beyond if you want or set that at max content, whichever, heaps of options and that's partly why our discussions have resulted in different code to everyone else's, more content adjustability.

 

[Ricardo]

Bill Would this pcb work or need to work with an after market ecu? I have a Haltec sprit 500 installed

Steve_tme when would be your next tuning run to the ACT?

 

[Kaldek]

Bill Would this pcb work or need to work with an after market ecu? I have a Haltec sprit 500 installed

You probably wouldn't need that PCB if your Haltech had a spare digital input. Seems like your biggest hurdle is making sure your tuner knows how to activate E85 FlexFuel in that ECU and tune the car.

 

[BCX]

You probably wouldn't need that PCB if your Haltech had a spare digital input. Seems like your biggest hurdle is making sure your tuner knows how to activate E85 FlexFuel in that ECU and tune the car.

Yep, correct...

The PCB is only required for use with OEM ECU + edited ROM reflash. This is cheaper than folking out for a third party ECU that has flex already.

 

[jungle]

• The way around this: most Mitsubishi's have a spare analog-to-digital inputs (ie an input that can read a voltage rather than a certain signal). This input in our case is the secondary o2 sensor.

Hi @BCX

I use the second O2 sensor to log boost while tuning via a GM 3bar map sensor. I gather I'll loose this ability?

 

[BCX]

Yes, but if you want, we can recycle another adc input... Like baro.

In TE/TF magnas, they didn't include the sensor and locked the value to 101.5kpa.

this code exists in out Rom to lock this. So could do something like that?